Alginate-based Electrospun Research Articles

Alginate-Based Electrospun Nanofibers and the Enabled Drug Controlled Release Profiles: A Review.

Alginate is a natural polymer with good biocompatible properties and is a potential polymeric material for the sustainable development and replacement of petroleum derivatives. However, the non-spinnability of pure alginate solutions has hindered the expansion of alginate applications. With the continuous development of electrospinning technology, synthetic polymers, such as PEO and PVA, are used as co-spinning agents to increase the spinnability of alginate. Moreover, the coaxial, parallel Janus, tertiary and other diverse and novel electrospun fiber structures prepared by multi-fluid electrospinning have found a new breakthrough for the problem of poor spinning of natural polymers. Meanwhile, the diverse electrospun fiber structures effectively achieve multiple release modes of drugs. The powerful combination of alginate and electrostatic spinning is widely used in many biomedical fields, such as tissue engineering, regenerative engineering, bioscaffolds, and drug delivery, and the research fever continues to climb. This is particularly true for the controlled delivery aspect of drugs. This review provides a brief overview of alginate, introduces new advances in electrostatic spinning, and highlights the research progress of alginate-based electrospun nanofibers in achieving various controlled release modes, such as pulsed release, sustained release, biphasic release, responsive release, and targeted release.

Fabrication of Alginate-Based Electrospun Nanofibers for Carbon Dioxide Removal

A fabrication of eco-friendly and low-cost adsorbent materials is reported for CO2 removal. Alginate nanofibers (NFs) adsorbents were prepared by incorporating poly(vinyl alcohol) (PVA) into alginate solutions via electrospinning technique from alginate biopolymers. Smooth-surfaced Alg/PVA NFs were obtained with a specific surface area of 9.197 m2 g–1. Zeolite (Z) was impregnated into polymer solutions to enhance the properties and performances of alginate nanofibers. Alg/PVA/Z NFs appeared to be rougher with a specific surface area of 25.998 m2 g–1. Both adsorbents offered great potential for CO2 adsorbent in the future. The adsorption isotherms of Alg/PVA NFs followed the Langmuir model with optimum CO2 adsorption capacity of 3.286 mmol g–1 and Alg/PVA/Z NFs followed Dubinin-Radushkevich model with optimum CO2 adsorption capacity of 10.710 mmol g–1.

Chitosan-functionalized sodium alginate-based electrospun nanofiber membrane for As (III) removal from aqueous solution

Environment-friendly chitosan-modified-poly(vinyl alcohol) or (PVA)/sodium alginate (SA) electrospun nanofiber membrane (ENM) adsorbent was prepared for the removal of As(III) from an aqueous solution. The chitosan(CS)-functionalized-PVA/SA ENM (CS-f-PVA/SA) was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and X-Ray diffraction (XRD). The CS-f-PVA/SA ENM showed the maximum As (III) adsorption capacity at neutral pH (540.40 mg g−1). The adsorption experiments were conducted by varying the initial pH of the arsenic solutions and also in the presence of different coexisting anions, such Cl- and F-, SO42−, and PO43−. Moreover, the kinetic studies were performed to depict the rate of As(III) sorption onto CS-f-PVA/SA ENM. The As(III) adsorption reached equilibrium within 90 min, which well fitted to the pseudo-second-order kinetic model. The initial pH of arsenic solutions greatly affected the adsorption efficiency but the presence of competing anions in arsenic solutions showed a moderate effect on the arsenic adsorption. The FTIR and XRD analyses suggest that–NH2, –OH, and C–O functional groups of CS-f-PVA/SA ENM are responsible for As(III) uptake. The prepared CS-f-PVA/SA ENM can be easily regenerated using 0.003 M NaOH, and the As(III) removal rate was still above 90–50% after ten successive adsorption-desorption cycles. Thus, such a nanofiber-based adsorbent is quite promising for the removal of As(III) from potable water and can be beneficial in combating the current challenges of arsenic pollution.

Effect of sodium alginate molecular structure on electrospun membrane cell adhesion

Alginate-based electrospun nanofibers prepared via electrospinning technique represent a class of materials with promising applications in the biomedical and pharmaceutical industries. However, to date, the effect of alginate molecular mass and block composition on the biological response of such systems remains to some extent unclear. As such, in the present work, three alginates (i.e., M.pyr, L.hyp, A.nod) with different molecular features are employed to prepare nanofibers whose ability to promote cell adhesion is explored by using both skin and bone cell lines. Initially, a preliminary investigation of the raw materials is carried out via rheological and zeta-potential measurements to determine the different grade of polyelectrolyte behaviour of the alginate samples. Specifically, both the molecular mass and block composition are found to be important factors affecting the alginate response, with long chains and a predominance of guluronic moieties leading to a marked polyelectrolyte nature (i.e., lower dependence of the solution viscosity upon the polymer concentration). Subsequently, physically crosslinked alginate nanofibrous mats are first morphologically characterized via both scanning electron and atomic force microscopy, which show a homogenous and defect-free structure, and their biological response is then evaluated. Noticeably, fibroblast and keratinocyte cell lines do not show significant differences in terms of cell adhesion on the three mats (i.e., 30–40% and 10–20% with respect to the seeded cells, respectively), with the formers presenting a greater affinity toward the alginate-based nanofibers. Conversely, both the investigated osteoblast cells are characterized by a distinct behaviour depending on the alginate type. Specifically, polysaccharide samples with an evident polyelectrolyte nature are found to better promote cell viability (i.e., cell adhesion in the range 15–36% with respect to seeded cells) compared to the ones displaying a nearly neutral behaviour (i.e., cell adhesion in the range 5–25% with respect to seeded cells). Therefore, the obtained results, despite being preliminary, suggest that the alginate type (i.e., molecular structure properties) may play a topical role in conditioning the efficiency of healing patches for bone reparation, but it has a negligible effect in the case of skin regeneration.

Encapsulating bacteria in alginate-based electrospun nanofibers.

Encapsulation technologies are imperative for the safe delivery of live bacteria into the gut where they regulate bodily functions and human health. In this study, we develop alginate-based nanofibers that could potentially serve as a biocompatible, edible probiotic delivery system. By systematically exploring the ratio of three components, the biopolymer alginate (SA), the carrier polymer poly(ethylene oxide) (PEO), and the FDA approved surfactant polysorbate 80 (PS80), the surface tension and conductivity of the precursor solutions were optimized to electrospin bead-free fibers with an average diameter of 167 ± 23 nm. Next, the optimized precursor solution (2.8/1.2/3 wt% of SA/PEO/PS80) was loaded with Escherichia coli (E. coli, 108 CFU mL-1), which served as our model bacterium. We determined that the bacteria in the precursor solution remained viable after passing through a typical electric field (∼1 kV cm-1) employed during electrospinning. This is because the microbes are pulled into a sink-like flow, which encapsulates them into the polymer nanofibers. Upon electrospinning the E. coli-loaded solutions, beads that were much smaller than the size of an E. coli were initially observed. To compensate for the addition of bacteria, the SA/PEO/PS80 weight ratio was reoptimized to be 2.5/1.5/3. Smooth fibers with bulges around the live microbes were formed, as confirmed using fluorescence and scanning electron microscopy. By dissolving and plating the nanofibers, we found that 2.74 × 105 CFU g-1 of live E. coli cells were contained within the alginate-based fibers. This work demonstrates the use of electrospinning to encapsulate live bacteria in alginate-based nanofibers for the potential delivery of probiotics to the gut.

Nanocomposite alginate-based electrospun membranes as novel adsorbent systems

Alginate-based membranes embedding zinc oxide nanoparticles are prepared via electrospinning and exploited as biosorbent materials. The mats exhibit a uniform texture characterized by the presence of nanofibers with an average diameter of 100 nm and interconnected voids of 140 nm average size. UV–vis spectrophotometric tests were performed to evaluate the membrane uptake/release performances by employing aqueous solutions of Methylene Blue (MB) and Congo Red (CR), chosen as model probes of basic and acidic type, respectively. Isotherm kinetics and equilibrium data are fitted with theoretical models to acquire information on the process mechanisms and rates. At low dosage, the mats show comparable adsorption capacity toward both dyes with limited selectivity for the cationic one suggesting that the process is conditioned by the macroporous structure of the membranes. Moreover, a good reusability for achieved for MB after simple washing steps in deionized water. Remarkably, the desorption efficacy under physiological-like conditions turn out to be very high for MB but reduced for CR indicating that the release process is affected by ionic interactions. Based on the results, the electrospun membranes reveal potential as innovative, low-cost, and versatile absorbent platforms to be used in drug delivery applications as well as in purification processes.

An alternative way to encapsulate probiotics within electrospun alginate nanofibers as monitored under simulated gastrointestinal conditions and in kefir

•In this study, Lactobacillus paracasei KS-199 was encapsulated within alginate-based electrospun nanofiber mats possessing uniform, well-defined, smooth and bead-free structure with an average size of 305 nm in diameter. Enhanced protection ability of the mats was observed in thermal degradation assays (weight loss from 93.4 to 84.5%). Probiotic and in situ viabilities were determined in simulated gastrointestinal and in vitro conditions, respectively, demonstrating that nanoencapsulation of the strain could enhance its survival in simulated gastric juice (the viability rate from 64.1 to 70.8 log cfu/mL) and improved its viability/survival (from 6.65 to 7.38 log cfu/mL) in kefir, respectively. Inoculation of kefir with encapsulated strain did not change the characteristic pseudoplastic flow behavior and viscoelastic nature (being predominantly elastic than viscous; G′ >G′′ values) of kefir. Given these results, it is possible to suggest that alginate can be an important tailor-made biopolymer playing an essential role for encapsulation of probiotics with increased viability.

Alginate-based electrospun core/shell nanofibers containing dexpanthenol: A good candidate for wound dressing

The skin prevents infection and contamination entering the body, and wound dressings are one of the most serious tools in wound healing. In the present work, the biocompatibility and swelling tendency of nanofibers increased by adding alginates to a polymer solution is investigated. Glutaraldehyde was used in different methods to strengthen nanofibers, and it was found that a better cross-link was made from the combination of glutaraldehyde with the polymer solution before electrospinning. As the use of drug accelerates the healing process, dexpanthenol was added to the polymeric composition of polyvinyl alcohol (PVA) and sodium alginate (SA) using a blending method. The resulting composition was then used as the core of the nanofibers, and drug release was controlled by different shells. The results showed that the presence of chitosan 1% (w/v) in the shell side of nanofibers helped better control the drug release. Also, the drug release from dexpanthenol-loaded wound dressing followed the Fickian diffusion mechanism with the Korsmeyer-Peppas model. MTT analysis and cell culture indicated that dexpanthenol-loaded PVA/SA/Triton-Chitosan nanofibers not only were nontoxic to the fibroblast cells but also appropriately affected the cellular attachment and morphology. It was revealed that PVA/SA/Triton-Chitosan nanofibers could be used for tissue engineering applications.

Alginate-Based Electrospun Membranes Containing ZnO Nanoparticles as Potential Wound Healing Patches: Biological, Mechanical, and Physicochemical Characterization.

In the present work, alginate-based mats with and without ZnO nanoparticles were prepared via an electrospinning technique and subjected to a washing-cross-linking process to obtain highly stable products characterized by thin and homogeneous nanofibers with a diameter of 100 ± 30 nm. Using a commercial collagen product as control, the biological response of the prepared mats was carefully evaluated with particular attention paid to the influence of the used cross-linking agent (Ca2+, Sr2+, or Ba2+ ions) and to the presence of nanofillers. Fibroblast and keratinocyte cultures successfully proved the safety of the prepared alginate-based mats, whereas ZnO nanoparticles were found to provide strong antibacteriostatic and antibacterial properties; above all, the strontium- and barium-cross-linked samples showed performances in terms of cell adhesion and growth very similar to those of the commercial collagen membrane despite them showing a significantly lower protein adsorption. Moreover, the mechanical and water-related properties of the strontium-cross-linked mats embedding ZnO nanoparticles were proven to be similar to those of human skin (i.e., Young modulus of 470 MPa and water vapor permeability of 3.8 × 10-12 g/m Pa s), thus proving the ability of the prepared mats to be able to endure considerable stress, maintaining at the same time the fundamental ability to remove exudates. Taking into account the obtained results, the proposed alginate-based products could lead to harmless and affordable surgical patches and wound dressing membranes with a simpler and safer production procedure than the commonly employed animal collagen-derived systems.

Preparation of composite alginate-based electrospun membranes loaded with ZnO nanoparticles

In the present work alginate-based nanofibrous membranes embedding zinc oxide nanoparticles (ZnO-NPs) were prepared via electrospinning technique. ZnO-NPs were synthesized by means of a “green” sol-gel method by using alginate itself as stabilizing agent and characterized through UV–vis spectroscopy, thermogravimetric and morphological analysis. Formulations containing sodium alginate, poly(ethylene oxide) and ZnO-NPs were rheologically studied to identify the most suitable ones to be electrospun; alginate molecular structure played an important role on the solution spinnability due to the polysaccharide capability to establish electrostatic interactions and hydrogen bonds with ZnO-NPs. An innovative washing-crosslinking protocol was developed to obtain stable products which composition was assessed using Fourier Transform InfraRed spectroscopy and thermogravimetric analysis. Morphological investigation combined with EDX spectroscopy proved the obtained mats were highly porous and composed by thin homogenous nanofibers with a good distribution of the used nanofillers, thus representing potential products for several purposes (e.g. biomedical, pharmaceutical and environmental applications).

Drug-Loaded Halloysite Nanotube-Reinforced Electrospun Alginate-Based Nanofibrous Scaffolds with Sustained Antimicrobial Protection.

Halloysite nanotube (HNT)-reinforced alginate-based nanofibrous scaffolds were successfully fabricated by electrospinning to mimic the natural extracellular matrix (ECM) structure which is beneficial for tissue regeneration. An antiseptic drug, cephalexin (CEF)-loaded HNT, was incorporated into the alginate-based matrix to obtain sustained antimicrobial protection and robust mechanical properties, the key criteria for tissue engineering applications. Electron microscopic imaging and drug release studies revealed that CEF had penetrated into the lumen space of the HNT and also deposited on the outer walls, with a total loading capacity of 30 wt %. Moreover, the diameter of alginate-based nanofibers of the scaffolds ranged from 40 to 522 nm with well-aligned HNTs, resulting in superior mechanical properties. For instance, the addition of 5% (w/w) HNT improved the tensile strength (σ) and elastic modulus by 3-fold and 2-fold, respectively, compared to those of the alginate-based scaffolds without HNT. The fabricated scaffolds exhibited remarkable antimicrobial properties against both Gram-negative and Gram-positive bacteria, and the cytotoxicity studies confirmed the nontoxicity of the fabricated scaffolds. Drug release kinetics showed that CEF inside HNTs diffuses within 24 h and that the diffusion of the drug is delayed by 7 days once the CEF-loaded HNTs are incorporated into the alginate-based nanofibers. These fabricated alginate-based electrospun scaffolds with enhanced mechanical properties and sustained antimicrobial protection hold great potential to be used as artificial ECM scaffolds for tissue engineering applications.

Studies of magnetic alginate-based electrospun matrices crosslinked with different methods for potential hyperthermia treatment

The magnetic electrospun mats were lately established as an innovative biomaterial for hyperthermic cancer treatment. Unlike those surface-modified magnetic nanoparticles that may not firmly adhere onto the tumor for long-term duration, the magnetic mats with nanofibrous structure can promote cell adhesion and kill the tumor directly within an alternating magnetic field. However, most magnetic electrospun mats were fabricated using non-biodegradable polymers and organic solvents, causing the problems of removal after therapy and the suspected biotoxicity associated with residual solvent. Alginate (SA) was utilized in this investigation as the main material for electrospinning because of being biodegradable and water-soluble. The alginate-based electrospun mats were then treated by an ionic or a covalent crosslinking method, and then followed by chelation with Fe2+/Fe3+ for chemical coprecipitation of Fe3O4 magnetic nanoparticles. Significant less cytotoxicity was noted on both liquid extracts from the ionic-crosslinked (Fe3O4-SA/PEO) and covalent-crosslinked (Fe3O4-SA/PVA) magnetic electrospun mats as well as the surface of Fe3O4-SA/PVA. In vitro hyperthermia assay indicated that the covalent-crosslinked magnetic alginate-based mats reduced tumor cell viability greater than Fe3O4 nanoparticles. Such magnetic electrospun mats are of potential for hyperthermia treatment by endoscopic/surgical delivery as well as serving as a supplementary debridement treatment after surgical tumor removal.

Histological evaluation of wound healing performance of electrospun poly(vinyl alcohol)/sodium alginate as wound dressing in vivo

Poly(vinyl alcohol)/sodium alginate nanofibrous mats were produced by electrospinning method at optimum process parameters. Evaluation of alginate-based electrospun nanofibrous mats as a wound dressing material and their comparison to commercially available wound dressings produced with conventional methods were carried out in vivo. Tissue specimens were examined histopathologically on 4th, 6th, 15th, 21st postoperative days. In contrast to other dressings it was observed that nanofibrous mat could survive on the wound crust in early stages of healing. In terms of epithelization, epidermis characteristics, vascularization and formation of hair follicles, nanofibrous mat showed the best healing performance. This could be explained with presence of nanofibrous mat acting as an artificial skin on the wound region until new tissue regenerated.